(1) Field of the Invention
The present invention relates to a method for preparing epichlorohydrins from allyl chlorides and an alkyl hydroperoxide.
(2) Description of the Prior Art
As manufacturing techniques of epichlorohydrins, there are known the chlorohydrin process, the chlorination process of allyl alcohol and the peroxide process.
In the chlorohydrin process, an allyl chloride and a chlorohydrin are used as a raw material and as an oxidizing agent, respectively, and therefore the amount of chlorine used therein is too great. In the allyl alcohol process, raw materials are expensive.
In the peroxide process, tert-butyl hydroperoxide, ethylbenzene hydroperoxide, cumene hydroperoxide, hydrogen peroxide, a peracid, etc. are used as oxidizing agents. Exemplary cases where homogeneous catalysts are used in this process are disclosed in Japanese Patent Publication Nos.19609/'73 and 17649/'70. In this process, however, the recovery of the catalyst is intricate and difficult, since it is dissolved in the reaction product mixture. There is another technique for synthesizing epichlorohydrin in which epoxidation of propylene or allyl chloride is carried out with the aid of an alkyl hydroperoxide in the presence of a solid catalyst, and this synthetic technique is described in Japanese Patent Laid-Open No. 55609/'74, Japanese Patent Publication No. 30049/'75 and J. Catalysis, 31, P. 438 (1973). In these publications, the reaction is performed by using stable tert-butyl hydroperoxide as the hydroperoxide with 2,6-di-tert-butyl-4-methylphenol added as a stabilizer, so that epichlorohydrin is obtained in a selectivity of 73% (on the basis of the hydroperoxide). However, when ethylbenzene hydroperoxide is used, the selectivity is 55%, and in the case of using cumene hydroperoxide, the selectivity is no more than 8%.
In Japanese Patent Laid-Open No. 7908/'77, there is disclosed epoxidation of olefins by using a solid catalyst formed by esterifying a metal-silicon oxide with a primary or secondary aliphatic alcohol. The selectivity to the desired epoxy compound seems to be improved by using the catalyst, but no description is made with regard to epichlorohydrins. The use of the catalyst is effective in the epoxidation of propylene.
Japanese Patent Publication No. 40526/'79 discloses a process in which a titanium-silica catalyst is brought into contact with a silylating agent in the production of oxirane compounds by the reaction of hydroperoxides with olefins. Allyl chloride is also illustrated as a variation of the olefins used as the raw material, but no specific description is made with the synthesis of epichlorohydrins.